Evaluation of Opuntia stricta mucilage as sustained release excipient in diclofenac sodium matrix tablet formulations
Over the last few decades, plant derived polymers have received increasing attention due to their diverse pharmaceutical applications including modified and controlled drug delivery. Among these natural polymers, mucilages and gums are versatile excipients for pharmaceutical formulation. The main objective of the present study was to evaluate cactus (Opuntia stricta) mucilage as a matrix forming polymer for sustained release tablet formulations using diclofenac sodium as a model drug. The mucilage from cactus cladode was extracted using distilled water as extracting solvent and ethanol as mucilage precipitant. The mucilage powder was characterized for its physical properties. A 1% w/v solution of the mucilage in water gave a pH of 6.40 ensuring low irritability potential when used in uncoated tablets. Evaluation of the powder flow profile demonstrated fair flow showing the need for incorporating other compressible excipients or using granulation to enhance the flow pattern. The solubility and swelling power of the O. stricta were generally low at low temperature (20 ºC), but increased significantly at higher temperature (85 ºC) (p < 0.05). The percentage moisture sorption ranged from 7.61% at 15% to 79.9% at 100% relative humidity (RH). The granules prepared with water as granulating solvent showed excellent flow property. The crushing strength of wet granulated formulations was higher than directly compressed formulations. The in vitro dissolution study demonstrated that both directly compressed and wet granulated formulations of O. stricta mucilage effectively sustained diclofenac release for over 12 h even at a lower concentration of 10%. However, granulation showed a better matrix performance for sustaining the drug release. All the formulations showed good linearity with respect to Korsmeyer-Peppas equation with 0.45 ≤ n ≤ 0.89 indicating that, non Fickian diffusion was the predominant mechanism of drug release from these formulations. So, O. stricta mucilage can be used as alternative pharmaceutical excipient in the formulation and manufacture of sustained release matrix tablets.
Keywords: Opuntia stricta mucilage, direct compression, in vitro drug release, wet granulation, matrix tablets